Heat pumps · Error codes · Ariston
2P5Ariston · NIMBUS NET R32 control platform (shared error list)
2P5 on an Ariston NIMBUS NET R32 control platform: Electric heater thermostat (automatic reset)
Short answer
On an Ariston heat pump, 2P5 means: Electric heater thermostat (automatic reset). The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Electric heater thermostat (automatic reset).
Part involved: backup heater safety thermostat (auto reset).
Likely causes:
- Main circulation pump not activating.
- Low flow.
- Safety thermostat condition / cabling.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
What you can check
- Note the error code shown on the Sensys HD interface and contact the installer / Ariston service.
What the engineer will check
- Check activation of the main circulation pump.
- Check the flow via flow meter reading (parameter 13.9.3).
- Check the safety thermostat and cabling.
Who to ask for: heat pump controls / hydronics.
Certification: Competent heating engineer; electrical competence for wiring checks.
What you might notice
Sources
- NIMBUS PLUS M NET R32 - Technical instructions for installation and maintenance (UK) - codes 3301719 3301720, doc 420000656201 EN ↗ · 420011311701 - 03/2024 · page 71 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026